Imvertor was invented by and built for the Dutch Cadastre ("Kadaster"). Kadaster has a service organization ("modellenbureau") which is charge of all information models that are created and maintained by Kadaster. You can reach this service organisation by email: modellen dot bureau at kadaster dot nl.
After some time VNG/KING (Association of Netherlands Municipalities, dept. of Standardisation) decided to use the Kadaster Imvertor framework to streamline their XML schema development. VNG/KING also added new software fragments to suit their particular needs.
Recently Geonovum has decided to join the community, and decided to start off with the TNO/BRO (Key register for the Dutch Subsurface).